Method for preparing sulphonate salts

ABSTRACT

The invention concerns a method for preparing sulphonate salts, alkaline or alkaline-earth, corresponding to anion of general formula (I):(R—CF 2 —SO 3   − ) n , through alkaline hydrolysis of sulphonyl chlorides corresponding to formula (II). The invention is characterized in that it comprises at least a step which consists in alkaline hydrolysis of sulphonyl chloride carried out in the presence of a phase-transfer agent.

This application is a 371 of PCT/FR00/01832 filed Jun. 29, 2000.

The present invention relates to a process for preparing sulfonate saltsvia alkaline hydrolysis of the corresponding sulfonyl chlorides.

The conventional method for obtaining a sulfonate salt from a sulfonylchloride consists in carrying out the hydrolysis of the sulfonylchloride using inexpensive bases, such as alkali metal or alkaline earthmetal carbonates or hydroxides, e.g. sodium hydroxide. However, theliterature includes only a few cases of alkaline hydrolysis of sulfonylchloride by this kind type of bases: mention may be made, among theserare examples, of R. N. Haszeldine (J. Chem. Soc., 2901 (1955)), whodescribes a quantitative alkaline hydrolysis of trifluoromethanesulfonylchloride by 15% sodium hydroxide, i.e. by a sodium hydroxide solutionwith a relatively low concentration.

It should be noted that the hydrolysis of a sulfonyl chloride, and inparticular of a (per)fluorinated sulfonyl chloride, is generallydifficult to carry out, especially because of the covalent nature of theSO₂—Cl bond, and in view of the fact that these substrates are generallybetter oxidizing agents than electrophiles. In this respect, it shouldactually be emphasized that similar compounds, such as sulfuryl chlorideSO₂Cl₂, are commonly used as chlorinating agents. Generally, sulfonylchlorides are therefore often not very reactive with respect to thehydrolysis reaction.

Consequently, the problem encountered during the alkaline hydrolysis ofa sulfonyl chloride is as follows: the hydrolysis reaction of thesulfonyl chloride is a reaction which, on the one hand, intrinsicallyhas a significant exothermic nature and which, on the other hand, ischaracterized by significant inertia, due to the fact that the reactantsare present in two, separate phases, which accentuates the exothermicityof the reaction. This inertia does not give rise to any complicationduring the hydrolysis of small amounts and/or with dilute alkalinesolutions, such as those described in the literature; however, it raisesreal safety problems as soon as attempts are made to carry out thereaction with higher concentrations of base and/or on industrialamounts: this is because the inertia of the reaction then leads to abuildup of sulfonyl chloride during the reaction which can represent upto 20% of the amount of sulfonyl chloride introduced and which, inconjunction with the high intrinsic exothermicity of the hydrolysisreaction, can lead to runaway of the reaction.

To avoid such problems, the only currently existing solution consists incarrying out the alkaline hydrolysis by means of a dilute hydroxidesolution, which involves removing the water by additional distillationstages, harmful in terms of industrial productivity.

The aim of the present invention is specifically to provide a method forthe preparation of sulfonate salts which are simultaneously inexpensive,fast and reliable, by carrying out the alkaline hydrolysis of a sulfonylchloride with a concentrated basic solution, but while avoiding theproblem of buildup of the sulfonyl chloride due to the inertia of thereaction.

More specifically, the resent invention relates to a process forpreparing an alkali metal or alkaline earth metal sulfonate saltcorresponding to the anion of general formula (I):

R—CF₂—SO₃ ³¹  (I),

wherein R is:

(a) a hydrogen atom;

(b) a halogen, preferably a light halogen (that is to say, with anatomic number at most equal to that of chlorine), and more preferablyfluorine;

(c) an alkyl chain optionally substituted by one or more halogenatom(s);

(d) an alkenyl chain optionally substituted by one or more halogenatom(s);

(e) an aryl group which is optionally substituted by one or more halogenatom(s) and which can comprise one or more heteroatoms;

(f) an arylalkyl group optionally substituted by one or more halogenatom(s), it being possible for the aryl group to comprise one or moreheteroatoms; or

(g) a sulfonyl heavy halide group,

with it being possible for R, when it is a group as defined in (c), (d),(e) and (f), to be substituted by a sulfonyl heavy halide group,

said sulfonate salt being obtained from a sulfonyl chloride of generalformula (II)

R—CF₂—SO₂Cl

wherein R is as defined above,

said process comprising at least one stage of alkaline hydrolysis of thesulfonyl chloride (II) in the presence of at least one compound actingas a phase transfer agent.

The R group present in the sulfonyl chlorides employed in the process ofthe invention is preferably an electron-withdrawing group, that is tosay a radical with a σp value generally greater than 0, preferablygreater than 0.1 and advantageously at least equal to 0.5.

R is advantageously a fluorine atom or a perfluoroalkyl radical R_(f)optionally substituted by a sulfonyl heavy halide group.

Within the meaning of the invention, a sulfonyl heavy halide grouprefers to a group carrying a sulfonyl halide functional group or ahalogen and chlorine or bromine and preferably chlorine and for whichthe carbon atom adjoining the sulfur atom is perhalogenated by halogenswith an atomic number at most equal to that of chlorine and ispreferably perfluorinated. This group can have from 1 to 10 carbonatoms.

Thus, the claimed process s especially suitable for preparing alkalimetal or alkaline earth metal sulfonate salts which exhibit at leastone, indeed even two, sulfonyl group(s), the carbon atom(s) adjoiningthe sulfur atom(s) being perfluorinated.

These bisulfonate compounds can be useful in particular for preparingpolymeric compounds or alternatively cyclic compounds, when the numberof linking units separating the two sulfonate functional groups is 2, 3or 4. The linking units which separate the two sulfonate functionalgroups are advantageously CF₂ linking units.

Furthermore, it should be pointed out that the, carbonaceous chainspresent in the sulfonyl chlorides employed in the process of theinvention are preferably saturated chains, so as in particular to avoidphenomena of untimely polymerization. Furthermore, the sulfonylchlorides employed in the process of the invention generally comprise atotal carbon atom number advantageously of less than 30.

Within the meaning of the present invention, the term “phase transferagent” denotes a compound capable of compensating for the inertia of thehydrolysis reaction and of preventing the problem of the buildup of thesulfonyl chloride due to the fact that the reactants are found in twoseparate phases.

This phase transfer agent may be either of cryptant type, such as crownethers, or of onium type, or an alcohol.

Thus, according to a first aspect of the invention, the role of phasetransfer agent is played by a phase transfer agent of onium cation type.

Oniums are compounds with names, in the nomenclature, comprising thesequence of letters “onium” as affix, generally as suffix. They aresemimetallic compounds, in particular from the nitrogen column and fromthe sulfur column, which are sufficiently substituted to carry apositive charge. Thus, the atoms from the nitrogen column, when they aresubstituted four times by a hydrocarbonaceous radical, constituteoniums.

Thus, quaternary ammoniums or quaternary phosphoniums can be used asphase transfer agent.

Sulfoniums (tertiary in their case) themselves also constitute phasetransfer agents, but they are less advantageous, since they arerelatively more unstable than the others.

The oniums used as phase transfer agent are known to a person skilled inthe art.

The most commonly used are tetraalkylammoniums and tetraalkyl- ortetraphenylphosphoniums. The latter exhibit, however, the disadvantageof being relatively expensive.

The preferred phase transfer agents among said, onium cations aretetraalkylammonium comprising saturated, unsaturated or aromatichydrocarbonaceous chains comprising a total of 4 to 28 carbon atoms,preferably of 4 to 16 carbon atoms.

To avoid β-elimination reactions, the most widely used onium istetramethylammonium, although it is relatively unstable fromapproximately 150° C.; mention may also be made ofbenzyltrimethylammonium.

The onium cation is preferably employed in an amount representing from 1to 20 mol % with respect to the total number of sulfonyl chloridefunctional group(s) present on the compound of formula II, morepreferably from 1 to 5 mol %.

According to a second aspect of the invention, which is a preferredembodiment, an alcohol, in particular a linear or branched and aliphaticor aromatic alcohol, comprising from 1 to 10 carbon atoms, preferablymore than 2 carbon atoms, is used as phase transfer agent, the mostpreferably used alcohol being selected from isopropanol, ethanol, benzylalcohol, isobutanol, n-propanol and sec-butanol.

In fact, any alcohol is suitable as phase transfer agent according tothe present invention, insofar as it is incapable of participating inside reactions, in particular in the formation of an ether in asufficient amount to threaten the reliability of the process.

In this respect, it is surprising to find that a primary or secondaryalcohol can be employed in the basic hydrolysis process of theinvention. This is because the sulfonyl chloride employed is generally abetter oxidizing agent than electrophile, which should lead to theoxidation of the alcohol employed, very particularly in the context ofthe use of perfluorinated sulfonyl chlorides, the oxidizing nature ofwhich is very pronounced. Furthermore, it should be emphasized that,among the alcohols preferably employed, isopropanol is known as being agood reducing agent.

Whatever its nature, the alcohol used is preferably employed in aproportion of 0.05 to 1 molar equivalent with respect to the number ofsulfonyl chloride functional group(s) present on the compound of formulaII, more preferably in a proportion of 0.1 to 0.2 molar equivalent.

Said alcohol used as phase transfer agent can optionally be partiallypresent in the form of the alkoxide ion in the basic hydrolysis medium.

The term “alkaline hydrolysis” is understood to denote, within themeaning of the present invention, hydrolysis by means of a basicsolution of an alkali metal or alkaline earth metal hydroxide or of asolution of carbonate salts.

The alkali metal or alkaline earth metal hydroxide solutions which arevery particularly suitable for the present invention are solutions of ametal hydroxide of general formula III:

(M)(OH)_(n)  (III),

where

M is an alkali metal or alkaline earth metal, and preferably an alkalimetal; and

n is an integer:

equal to 1 in the case where M is an alkali metal,

equal to 2 in the case where M Is an alkaline earth metal, in a solventof hydroxylated type, the preferred solvent being water, a preferredalkali metal hydroxide solution being an aqueous sodium hydroxidesolution.

The solutions of carbonate salts according to the present invention aresolutions of a metal carbonate of general formula (IV):

(M)_(n)(CO₃)  (IV),

where

M is an alkali metal or alkaline earth metal, preferably an alkali metalor magnesium, and advantageously sodium; and

n is an integer:

equal to 1 in the case where M is an alkaline earth metal,

equal to 2 in the case where M is an alkali metal, in a solvent ofhydroxylated type, the preferred solvent being water.

As emerges from the examples presented below, the alcohol acts, like theonium salt, as a phase transfer agent between the alkaline solution andthe sulfonyl chloride, even if the nature of this phase transfer remainsto be specifically defined. Measurements of heats of reaction given offduring alkaline hydrolyses carried out in the presence of an alcohol inany case undoubtedly reveal a sharp reduction in the buildup of thesulfonyl chloride during the reaction in comparison with measurementscarried out in the absence of phase transfer agent: the presence ofalcohol leads to a marked decrease in the delay observed in theevolution of the heat of reaction, that is to say a substantial increasein the rate of the alkaline hydrolysis reaction.

The preferred process according to the invention comprises a stage ofgradual addition of sulfonyl chloride at atmospheric pressure to amixture comprising at least:

said alkaline solution of hydroxide or of carbonate, and

said phase transfer agent composed of a compound of cryptant type, of acompound of onium salt type or of an alcohol.

Preferably, the alkaline solutions are aqueous solutions and areemployed at concentrations of greater than 20% by mass, which makes itpossible to eliminate the stages of distillation of water. Furthermore,in order to be able to carry out correct stirring, this concentration,which should not be too high in order to avoid an excessively highviscosity, is more preferably between 20 and 30% by mass.

In order to carry out a quantitative reaction, whatever the nature ofthe base used, the base is generally employed in an amount close to thestoichiometry of the reaction, that is to say in an amount of the orderof two molar equivalents with respect to the number of sulfonyl chloridefunctional group(s) present on the compound of formula II,advantageously in a proportion of 1.8 to 2.5 molar equivalents, andpreferably in an amount equal to 2 molar equivalents, with respect tothe number of sulfonyl chloride functional group(s) present.

Whether an alcohol or an onium salt is used, it may be considered thatthe presence of the phase transfer agent makes it possible to decreasethe duration of the hydrolysis reaction by approximately 50%, which,first, improves the efficiency of the process but also makes it possibleto operate under enhanced conditions of safety by preventing theproblems related to the buildup of the sulfonyl chloride. Be that as itmay, as a result of the high intrinsic exothermicity of the reaction,the hydrolysis can be carried out while cooling the reaction mediumusing, for example, an ice bath. This is because it is generallypreferable for the temperature of the reaction medium to be maintainedbetween −10° C. and 50° C. during the alkaline hydrolysis. It isadvantageously preferable for this temperature not to exceed 30° C. Inthe specific case of the use of CF₃SO₂Cl in the alkaline hydrolysisstage, it is furthermore preferable for this temperature to remain.below 20° C., in particular as a result of the low boiling point (29°C.) of this compound. However, if it is desired to implement the processof the invention at temperatures greaer than or equal to the boilingpoint of the sulfonyl chloride used, it is possible to carry out thereaction at a pressure greater than atmospheric pressure, for example ina closed chamber, and generally, in this case, at the autogeneouspressure of the reaction medium at the temperature at which it isdesired to operate.

However, it should be clearly emphasized that the limitation on the risein the temperature is generally due essentially to the presence of aphase transfer agent, which limits the phenomena of buildup of thesulfonyl chloride, very particularly in the case of the use of largeamounts of reactant.

Furthermore, it should also be noted that the specific presence of thephase transfer agent makes it possible to carry out the process of theinvention on an industrial scale without risk of overheating or ofrunaway of the reaction. Thus, the amounts of sulfonyl chloride employedin the process of the invention can, in the general case, reach amountsof greater than 1000 mol, indeed even greater than 5000 mol.

It should also be noted that the process of the invention lends itselfto a continuous embodiment.

According to one aspect of the invention, the alkaline hydrolysisprocess makes It possible to obtain said sulfonate salt in solution,preferably in aqueous solution, for example for a direct use in situ ofsaid salt as reaction intermediate, in particular for the synthesis ofthe corresponding sulfonic acid, these operations coming within thecompetence of a person skilled in the art.

According to another aspect of the invention, the process of preparationof the sulfonate salt makes it possible to obtain the salt in the solidform, in particular by selective precipitation and/or by concentratingto dryness, for example for an optionally subsequent use of said salt asreaction intermediate, in particular for the synthesis of thecorresponding sulfonic acid, in a way also known per se.

The examples set out below illustrate the present invention. They aregiven by way of explanation of the description and should not under anycircumstances limit the scope thereof.

EXAMPLE 1

Buildup Profiles

Example 1 presents three type of buildup profile observed in the case ofthe alkaline hydrolysis of CF₃SO₂Cl by solutions (A), (B) and (C)characterized by the following compositions (the percentages indicatedcorrespond to percentages by mass):

(A): 30% aqueous sodium hydroxide solution

(B): 20% aqueous sodium hydroxide solution

(C): 20% aqueous sodium hydroxide solution+isopropanol (0.2 molarequivalent).

The buildup, expressed in kJ/mol, is calculated from the amount of heatgiven off by the hydrolysis reaction at the end of a time t: itcorresponds to the difference between the expected amount of heat givenoff and the amount of heat actually given off.

The results obtained are combined in Table 1 below:

TABLE 1 Buildup (kJ/mol) (C) Time Number moles (A) (B) 20% NaOH + (min)charged 30% NaOH 20% NaOH isopropanol 0 0 5 0.08 243 19.5 1.8 10 0.066237 29.6 2.2 30 0.33 221 73 7.3 40 0.42 210 82 8.7 60 0.66 204 105 26.380 0.88 188 149 32 125 1.38 150 136 13 150 1.6 74 69 11 180 2 63 60 11

Comparison of the profiles obtained with the solutions (A) and (B)(respectively 30% and 20% by mass aqueous sodium hydroxide solutions)shows the influence of the concentration of hydroxide on the buildup: infact, the buildups observed with a 30% by mass solution are more than200 kJ/mol from the beginning of the experiment and lasting throughoutthe first hour of the hydrolysis, which raises significant problems ofsafety, in particular when operating on industrial amounts, whereas,with a 20% solution, the buildup is lower by an order of magnitude fromthe start and, even on combining the delay due to the inertia of thereaction, the buildup finally only reaches maximum values of the orderof 150 kJ/mol, for a duration of approximately 40 minutes. Be that as itmay, these values nevertheless remain very high and the results obtainedwith the solution (C) (20% by mass aqueous sodium hydroxide solution andisopropanol (0.2 equivalent)) show the whole advantage of the presentinvention: the buildups observed in the presence of isopropanol aredecreased by an order of magnitude with respect to those produced withthe solution (B) devoid of phase transfer agent, and the maximum buildupobserved is only of the order of 30 kJ/mol, which greatly reduces therisks usually accompanying the use of concentrated alkaline solution.

The two following examples set out two processes for the preparation ofsodium trifluoromethanesulfonate (more commonly known as sodiumtriflate) by alkaline hydrolysis, using an alcohol as phase transferagent, according to the present invention.

EXAMPLE 2

Preparation of Sodium Triflate by Alkaline Hydrolysis in the Presence ofIsopropanol

120 g of 20% sodium hydroxide (i.e. 0.6 mol of NaOH) and 3.6 g ofisopropanol (0.06 mol) are charged to a 200 ml reactor. The addition oftrifluoromethanesulfonyl chloride (50.5 g, i.e. 0.3 mol) is carried outover 1 h 45 while maintaining the reaction medium at 25° C. by coolingwith a water/ice mixture.

After adding the reactant, the reaction medium is kept stirred for 30min and then acidified with a 36% HCl solution to a pH=6.

The homogeneous medium obtained is concentrated at 70° C. under 100 mbaruntil a weight of 162 g is obtained. The precipitate formed is filteredoff at 20° C.

The filtrate obtained is subsequently concentrated to dryness and 57 gof a white solid are obtained, which solid is composed of 43.3 g ofsodium trifluoromethanesulfonate (sodium triflate), 5.2 g of sodiumchloride and residual water.

EXAMPLE 3

Preparation of Sodium Triflate by Alkaline Hydrolysis in the Presence ofEthanol

48 g of 50% by mass aqueous sodium hydroxide (i.e. 0.6 mol NaOH) and 80ml of ethanol are charged to a 200 ml reactor. The addition oftrifluoromethanesulfonyl chloride (50.5 g, i.e. 0.3 mol) is carried outover 1 h 00 without exceeding 30° C. by cooling with a water/icemixture. The precipitation of NaCl is immediate. After addition, thereaction medium is kept stirred for 2 h and then cooled to 5° C. Theprecipitate is filtered off at this temperature (dry weight=17.3 g). Afiltrate weighing 125 g is obtained, which filtrate comprises 40.6 g ofsodium triflate and 0.8 g of sodium chloride.

The quantitative aspect of the reactions and in particular the speedwith which the reactions are carried out (overall reaction time of 2 h15 for Example 2 and of 3 h 00 for Example 3), and the completely safeaspect of the handling (temperature not exceeding 25° C. in Example 2and not exceeding 30° C. in Example 3), despite the high concentrationsof the sodium hydroxide solutions employed and the speed with which theaddition is carried out (1 h 45 for Example 2 and only 1 h 00 forExample 3), should be noted in these two examples.

EXAMPLE 4

Preparation of Sodium Triflate by Alkaline Hydrolysis in the Presence ofa Phase Transfer Agent of Onium Type

This final example relates to a process for the preparation of sodiumtriflate by alkaline hydrolysis according to the present invention usinga cation of onium type as phase transfer agent.

80 g of 30% aqueous sodium hydroxide (corresponding to 0.6 mol of NaOH)and 1.25 g of benzyltrimethylammonium chloride are placed in a 250 mlreactor. 50.5 g (0.3 mol) of trifluoromethanesulfonyl chloride aresubsequently added over 1 h 30 while stirring at ambient temperature.

After stirring for 2 hours the medium is filtered at 20° C.

The aqueous phase is composed of 46.1 g of sodium triflate (0.27 mol).

It may also here be observed that the overall reaction time issufficiently low (3 h 30) and that, even if the addition is carried outover only 1 h 30, the reaction is carried out at ambient temperaturewithout presenting safety problems.

What is claimed is:
 1. A process for producing an alkali metal oralkaline earth metal sulfonate salt corresponding to the anion ofgeneral formula (I): R—CF₂—SO₃ ⁻  (I), wherein R is: (a) a hydrogenatom; (b) a halogen; (c) an alkyl chain optionally substituted by one ormore halogen atom(s); (d) an alkenyl chain optionally substituted by oneor more halogen atom(s); (e) an aryl group which is optionallysubstituted by one or more halogen atom(s) and which can comprise one ormore heteroatoms; (f) an arylalkyl group optionally substituted by oneor more halogen atom(s), it being possible for the aryl group tocomprise one or more heteroatoms; or (g) a sulfonyl heavy halide group,with it being possible for R, when it is a group as defined in (c), (d),(e) and (f), to be substituted by a sulfonyl heavy halide group, saidsulfonate salt being obtained from a sulfonyl chloride of generalformula (II) R—CF₂—SO₂Cl wherein R is as defined above, said processcomprising at least one stage of alkaline hydrolysis of the sulfonylchloride (II) in the presence of at least one compound acting as a phasetransfer agent, said compound being either a cryptant, or a cation ofonium type, or an alcohol.
 2. The process as claimed in claim 1, whereinsaid phase transfer agent is an onium cation.
 3. The process as claimedin claim 2, wherein said onium cation is a tetraalkylanmionium cationcomprising saturated, unsaturated or aromatic hydrocarbonaceous chainscomprising a total of 4 to 28 carbon atoms.
 4. The process as claimed inclaim 2, wherein the onium used is benzyltrimethylammonium ortetramethylammonium.
 5. The process as claimed in claim 2, comprising 1to 20 mol % of onium salt with respect to the number of sulfonylchloride functional group(s) present on the compound of formula (II). 6.The process as claimed in claim 1, wherein said phase transfer agent isan alcohol.
 7. The process as claimed in claim 6, wherein said alcoholis a linear or branched and aliphatic or aromatic alcohol comprisingfrom 1 to 10 carbon atoms.
 8. The process as claimed in claim 6, whereinthe alcohol used is selected from the group consisting of isopropanol,ethanol and benzyl alcohol, isobutanol, n-propanol and sec-butanol. 9.The process as claimed in claim 6, comprising 0.05 to 1 equivalent ofalcohol with respect to the number of sulfonyl chloride functionalgroup(s) present on the compound of formula (II).
 10. The process asclaimed in claim 1, wherein the alkaline hydrolysis of the sulfonylchloride (II) is carried out by means of a base selected from the groupconsisting of alkali metal or alkaline earth metal hydroxides andcarbonates.
 11. The process as claimed in claim 10, wherein said base isa metal hydroxide.
 12. The process as claimed in claim 11, wherein themetal hydroxide is present in the form of a solution with aconcentration of greater than 20%.
 13. The process as claimed in claim11, wherein the metal hydroxide used is sodium hydroxide, potassiumhydroxide or lithium hydroxide.
 14. The process as claimed in claim 1,wherein the amount of base employed is from 1.8 to 2.5 molar equivalentswith respect to the number of sulfonyl chloride functional group(s)present on the compound of formula (II).
 15. The process as claimed inclaim 1, wherein the salt obtained is sodium triflate CF₃SO₃Na.
 16. Theprocess as claimed in claim 1, wherein said alkali metal or alkalineearth metal salt of general formula (I) is obtained in the form of anaqueous solution and is converted in situ to result in the correspondingsulfonic acid.
 17. The process as claimed in claim 1, wherein saidalkali metal or alkaline earth metal salt is obtained in the form of asolid.